Adverse reactions Flashcards
Malignant hyperthermia
- Mechanism of inheritence
- How often does it occur
- What is the gene that is encoded
Pharmacogenetic disease of skeletal muscle - autosomal dominant mutation chromosome 19 in the gene coding for the ryanodine receptor - thymidine instead of cytosine
incidence 1:5,000 -> 1:65,000 anaesthetics
Pathophysiology of malignant hyperthermia
Excess Ca2+ is released from the sarcolemma during muscle contraction, resulting in increased muscle metabolism with prolonged and intensified interaciton between actin and myosin, which is exothermic and thus leads to hyperthermia.
enhanced aerobic metabolism -> lactic acidosis -> accumulation of intra-mitochondrial calicum -> deconjugation of oxidative phosphorylation -> cytolysis.
What triggers malignant hyperthermia
It is triggered by suxamethonium (on the first exposure, frequently) and all volatiles except nitrous oxide (one may experience volatile anaesthesia two or three times before encountering this).
Timing of malignant hypertmia
FOllowign induction
Body temperature rises by 1 degree every 10 minutes
Clinical features of malignant hyperthemia
Hyperthermia
Jaw rigidity persists after sux has worn off - masseter spasm
Tachycardia and tachypnoea
Increased EtCO2
Increased O2 consumption
Profuse sweating
Hyperkalemia
Cyanosis
Generalised rigidity, increased muscle tone
Prolonged bleeding
Management of therapeutic hyperthermia
Stop procedure, stop anaesthetic
Give 100% Fio2 and hyperventilate
Active cooling
Block NMJ with non depolarising agent
Dantrolene - 20mg as rapid infusion and keep giving until features of resolution/ 2.5mg/kg every 5 minutes total dose 10mg/kg/day continuous infusion - most important as mortality drops from 70% to 5%
2g methylped
High urine output
Correct coagulopathy
Consider bicarbonate 2-4 mmol/kg
Beta blockers and lignocaine for arrhtyhmias
Furosemide and glucose-insulin for high K
DIC screening 6 hourly
